PRIME is the third worst in the battery degradation. How is yours holding up?

Discussion in 'Prime Fuel Economy & EV Range' started by Salamander_King, Jun 28, 2020.

  1. Salamander_King

    Salamander_King Senior Member

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    Here Are The Best And Worst Electric Cars In Terms Of Battery Degradation

    According to the article, they got the data from here. What can 6,000 electric vehicles tell us about EV battery health? | Geotab
    On a cursory reading, I did not find specifics on how they calculate the battery degradation on each model.
    Note: They specifically states that the battery degradation is not the same as vehicle range (distance the vehicle can travel on those kWhs) — which will fluctuate on a daily or trip-by-trip basis, depending on a number of factors including charge level, topography, temperature, auxiliary use, driving habits, and passenger or cargo load.

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    #1 Salamander_King, Jun 28, 2020
    Last edited: Jun 28, 2020
  2. john1701a

    john1701a Prius Guru

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    That article has already been proven very misleading. The method used for data collection was poorly considered... so bad in fact, I have continued my push to document "degradation" in great detail to address such claims.

    3 years (close to 46,000 miles now) into ownership, I'm still not seeing any. The same route driven the same way under the same conditions continues to deliver the same results... as this recent video clearly confirms:

     
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  3. Salamander_King

    Salamander_King Senior Member

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    I have not read the GeoTab page carefully yet, but on my first cursory pass, I did not find specifics on how they came up with the numbers on degradation. Did you find it somewhere?
     
  4. bisco

    bisco cookie crumbler

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    i do not understand the difference between degradation, range, miles/kwh and charge capacity
     
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  5. john1701a

    john1701a Prius Guru

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    Sorry, I don't remember details... since I turned focus to data collection instead. I believe the sampling was limited to first year of use, which really doesn't tell you anything. Somewhere in the mix I found a big chunk of the vehicles were fleet use, which doesn't reflect way ordinary consumers would drive. Obviously, that's useful data to fleet purchasers though. So, it does have a somewhat useful nature.
     
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  6. Salamander_King

    Salamander_King Senior Member

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    I finished reading the GeoTab page, but I still could not find what "Data" they analyzed to get the battery degradation matrix for each of 21 models in their analyses. Here is the excerpt from the page on data collection.

    We analyzed the battery health of 6,300 fleet and consumer EVs, representing 1.8 million days of data. From the telematics data processed, we have gained insight into how real-world conditions influence the battery health of electric vehicles, providing aggregated average degradation data for 21 distinct vehicle models, representing 64 makes, models, and years.
    Yeah, the data is from fleet and consumer, but they state it is the "telematics data", meaning something that can be transmitted from a car? But other than the Advanced model, PRIME had no telematics. And even with the Advanced model, what data can be transmitted that can be analyzed to determine battery degradation. As I commented above, it is not the EV range they are comparing. It leaves a big question mark as to how they concluded the reduction "in the amount of energy a battery can store, or the amount of power it can deliver."

    Edit: I just found out that GeoTab Go is the telematics data collection device they used to collect the data. It is an OBDII connected module that must collect driving and possibly charging data from the ECU.
     
    #6 Salamander_King, Jun 28, 2020
    Last edited: Jun 28, 2020
  7. Salamander_King

    Salamander_King Senior Member

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    According to the GeoTab page, battery degradation is not the range or miles/kwh, but it is a change in the battery’s condition or state of health (SOH) which starts with 100% SOH at first and over time deteriorate. SOH is a measure of how much energy the battery can deliver (kWh). So, it should be equal to the "capacity" in kWh that battery can take from charging. However, the company GeoTab provides no explanation of how an installed OBDII module (GeoTab Go) on 6300 vehicles were used to calculate the loss in SOH in each model of vehicles analyzed.

    Interestingly, according to their EV Battery Degradation tool, the PRIME 2017, 2018, and 2019 models at 8 mo shows a quite different SOH. 2019 has the lowest at 97.7% (2.3% loss) but 2018 is 99.9% (0.1% loss) and 2017 is 99.4% (0.6% loss) at the same 8 month point. The insideEVs article I posted is comparing only 2019 models, thus PRIME resulted in the 3rd worst. Should they compared 2018 models, PRIME may be in the top 10. Without statistics on data or what data and how the data was analyzed to come up to the SOH number, the tool has almost no useful meaning, IMHO.
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    #7 Salamander_King, Jun 28, 2020
    Last edited: Jun 28, 2020
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  8. jerrymildred

    jerrymildred Senior Member

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    Degradation is the disease. Charge capacity is the symptom of that disease. As the battery degrades, it will hold less energy.

    Miles/kWh is basically how frugal you are with your right foot. It's a function of the demands on the battery imposed by temperature, terrain, acceleration, deceleration, tire pressure, hvac settings, etc.

    Range is the product of capacity and miles/kWh. If the battery has 5 kWh available and you use 5 miles/kWh, your range will be 25 miles.
     
  9. mr88cet

    mr88cet Senior Member

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    That the Prius Prime would lose battery capacity quickly doesn’t surprise me at all, for two reasons:

    First, automotive Li-Ion batteries are only good for around 300-500 full charging cycles. Now that number goes up a lot when you do not charge them fully — from electrochemically 0% to 100% full. That, of course, is why the P.Prime and other EVs maintain 15% or larger charging margins.

    Nevertheless, the smaller the battery, the more cycling it’s going to get, for a given amount of EV driving, and the Prime’s battery is among the smallest.

    Relatedly, it is only forced-air cooled. Liquid cooling improves battery longevity greatly.

    Second, my 2017 Prime has lost quite a bit. It’s currently at 25 miles or so although it has dropped as low as 21, and started at around 35ish. However, that has not been anything close to the gradual decline we would expect of true electrochemical degradation. It drops and goes back up in steps, so I think it’s far more likely that the charging computer is increasing and decreasing the charging margins for fear of losing battery longevity, than that the battery cell are actually electrochemically degrading much (so far).

    We need to bear in mind that the Prius Prime was not intended to be used as a pure EV. They intended us to charge it once per day overnight, drive it for a while in EV mode, then automatically switch over to HV when the charge hits the EV/HV threshold. That, as opposed to me, who level-2 charges it two to three times per day! That’s not how they expected nor intended the ‘Prime to be used!
     
  10. jerrymildred

    jerrymildred Senior Member

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    That sounds like a good theory. But the numbers on @john1701a's videos alway have always shown an actual SOC of 83% when his car's display shows 100%. Also, the actual SOC when the ICE comes on hasn't changed over the years. If the theory was true, his 2017 would be showing something above 83% actual SOC at the start of his videos and something lower than 13-14% at the end of the EV range. I'l have to check mine to see how it looks.
     
  11. mr88cet

    mr88cet Senior Member

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    I picked up the OBD Fusion app a while back to see if I can confirm my theory, but I haven’t had a chance to try it yet.
     
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  12. jerrymildred

    jerrymildred Senior Member

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    I got that one recently, too. I've played with it a little. Takes a lot of time to get the display set up and you have to buy the PIDs for the Prime, but it looks really powerful.

    Also, I just discovered how easy it is to do screen recordings on the iPhone. (y)
     
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  13. Salamander_King

    Salamander_King Senior Member

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    SOC level for my 2017 PRIME never changed from 83% when full and 11-14% when EV range depleted for 2.5 years of use. But as @PiPLosAngeles suggested, if the SOC% is calculated based on voltage, it may not change even if the total kWh stored in the traction battery gets reduced over time and buffer amount changes, keeping the overall ratio in 83% to 13% for usable EV drive.

    That being said, it is just a theory. AFAIK, there is no proof that Toyota has any way to dynamically change the buffered margin to hide the degradation or protect the battery longevity, either way.
     
    #13 Salamander_King, Jun 30, 2020
    Last edited: Jun 30, 2020
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  14. jerrymildred

    jerrymildred Senior Member

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    Yup, just a theory. And, if Toyota chose such a short sighted way to mask the degradation, the more the BMS eats into that buffer that's supposed to slow the degradation, the faster the battery will degrade.

    If the car was getting into the battery preservation buffer, I'd think by now we'd be seeing complaints of people with high mileage '17s only getting 10-15 miles of EV instead of complaints that they only get the EPA estimate of 25. And again, EV range is totally worthless in comparing one Prime to another and only useful on the same car if you're careful to factor in the many things besides capacity that affect it. My 44k+ mile Prime (not terribly high mileage, admittedly) still takes 6+kWh to charge from 0 EV.
     
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  15. Salamander_King

    Salamander_King Senior Member

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    Only thing is that for the traction battery I think the high mileage is not so much of the factor for degradation as the years in use (or sometimes non-use).
     
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  16. jerrymildred

    jerrymildred Senior Member

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    Maybe. But Primes make a LOT of use of the battery in HV mode and those partial cycles add up. If the miles are 70 mph miles, then they won't have as much effect on the battery, but at 50 mph in HV mode, mine is in EV at least half the time.
     
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  17. john1701a

    john1701a Prius Guru

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    Under the right circumstances, those shallow & frequent draws can actually increase longevity. Think of it as stretching before strenuous exercise.
     
  18. Salamander_King

    Salamander_King Senior Member

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    Good point. I wounder if anyone have looked at difference in battery degradation on the same model of car with same years of use but different miles driven and same miles driven but different years of use? Would be interesting.
     
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  19. john1701a

    john1701a Prius Guru

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    My wife got her Prime just 2 months after mine. Driving pattern is different. Her Prime never carries the kayaks or bikes and never goes on the long trips (with 80 mph cruising) to Wyoming either.

    Someday, I will film the repeating route with hers. I can't for the next month or two though, since that road is now under construction.
     
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  20. jerrymildred

    jerrymildred Senior Member

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    I Hadn't thought of it that way. Whatever the case, they seem to be holding up well from what I've experienced and seen. And there's not much I can complain about when getting 60-70 mpg in 40-55mph city HV driving. :)
     
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